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Measurements of image quality in the lab (march 2002) 
and comaprison with the values obtained last year
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The measurements I have were taken last year (IMPB).
Since then, the orientation of the array (as viewed in ximtool) 
has changed by 180 degress (I have checked it again now).
The table below shows the measured fwhm (in pixels) for three 
representative images taken during commissioning last year (april 2001).


   Orientation              fwhm           Peter's measurements
 IMPB        UDAS     (a)   (b)   (c)                X     Y
---------------------------------------   --------------------  
top right   bot left   3.07  3.49  3.48   Bot Left  3.23   3.96    
top left    bot right  2.61  3.06  3.11   Bot Right 1.59   2.10 
bot left    top right  2.62  3.28  3.29   Top Right 1.55   1.77
bot right   top left   3.25  4.08  3.58   Top Left  2.22   2.90 

The fwhm was always higher in the top-left corner and smaller in the 
bottom-right. The difference in fwhm is ~0.5-1 pixel.

Now, although the magnitudes are similar (max tilt ~1 pix in fwhm),
the orientation is different (higher fwhm in the bottom-left).
Therefore could be the detector mount which is causing the tilt.

Cheers,
	Almu

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                   fwhm (pix)
                   center       bottom-right
                   x    y

r484889  -1000   9.90  7.71     8.40  7.48
r484890  -1100   8.72  6.56     7.69  6.29
r484891  -1200   8.07  6.05     6.70  5.74
r484892  -1300   6.47  5.04     5.42  4.10
r484893  -1400   4.39  3.98     4.03  2.81
r484894  -1500   3.29  3.27     2.81  1.58
r484895  -1600   2.48  2.70     2.12  1.18
r484896  -1700   2.06  2.51     1.75  1.08
r484897  -1800   1.81  2.33     1.93  1.38
r484898  -1900   1.97  2.33     2.51  2.24